Internal insulation of containers for liquids having lower boiling point than atmospheric temperature

ABSTRACT

842,719. Storing gases under pressure. LORENTZEN, H. L. Sept. 13, 1956 [Sept. 16, 1955], No. 28051/56. Class 8(2). A container for a liquefied gas such as methane is insulated by vapour formed from the liquid in passages 3 formed between lamellae 2, of metal, synthetic resin, paper or a woven material with a dark rough surface, stuck to the inner surface of the container wall 1. The axes of the passages 3 may be perpendicular to the wall 1 or oblique as shown and the passages are small in order to hinder the formation of convection currents and may be of circular, square or hexagonal cross-section. In Fig. 2, lamellae are shown which are so corrugated and joined that the main passages 3 are of circular section. Rectangular units of insulation or hexagonal units with frames 5, Fig. 4, may be formed. The passages may have constrictions or be covered with a net. Local groups of cells may intercommunicate. Specification 789,755 is referred to.

Nov. 1, 1960 H. L. LORENTZEN 2,958,442

INTERNAL INSULATION OF CONTAINERS FOR LIQUIDS HAVING LOWER BOILING POINT THAN ATMOSPHERIC TEMPERATURE Filed Aug. 29, 1956 FIG].

FIG.2.

FIG.5.

Unite tates Patent INTERNAL INSULATION OF 'CONTAINERS FOR LIQUIDS HAVING LOWER BOILING POINT THAN ATMGSPHERIC TED IPERATURE Hans Ludvig Lorentzen, Madserud Alle 5, Oslo, Norway Filed Aug. 29, 1956, Ser. No. 606,829

Claims priority, application Norway Sept. 16, 1955 '3 Claims. ((11. 220-63) The present invention relates to internal insulation in containers for liquids which have a lower boiling point than the atmospheric temperature, and where the outside of the containers is exposed to higher temperature than the boiling temperature of the liquid inside the tank.

In order to prevent or reduce the heat transfer from the surroundings to the liquid it is usual to insulate the container externally, and in certain cases also internally. The insulation material for internal insulation is liable to become brittle if there is any possibility of very low temperatures, and the properties of the insulation will be reduced by the formation of cracks in the material.

The present invention is based on the fact that conducting of heat through gases (Vapour) is difficult, and according to the invention the insulation consists of a layer of gas (vapour) against the wall of the container, retained by means of a system of pores.

Along the walls of the container lamellae are mounted, preferably perpendicularly to the wall and at a relatively small distance from one another. The lamellae are so formed that the space between the same is split up into a number of individual spaces or pores. At the end of the pores opening against the outer Wall, the temperature will be above the boiling point of the liquid, and the liquid consequently will be transformed into vapour. At the end of the pores opening against the liquid, the temperature will correspond to the condensation temperature of the vapour, and the temperature gradient will form an almost straight line from wall to liquid. The distance be tween the lamellae, i.e. the width of the pores, must be so small that practically no convection currents can occur which, in case would increase the heat transfer from wall to liquid. Convection currents may also be counteracted by placing a filling material in the pores.

Precautions must also be taken to prevent a convection current along the surface of the wall. This can be done in the simplest way by securing the lamellae to the wall by means of a layer of adhesive material, which thus closes the wall end of each pore. Groups of inter-communicating pores may, however, also be established.

Metal, plastic, paper or a woven material can be used for the lamellae, the thickness of the same being very small in order to reduce the heat transmission through the lamellae proper.

The reflecting power of the lamellae proper should be as small as possible, and should therefore have a dark and rough surface.

In order to check the creeping of the liquid inwardly along the walls of the lamellae it will also be advantageous to use a material in the lamellae which is not wetted by the liquid.

The cross-section of the pores formed between the lamellae may be of any desired shape. They may be circular, square, hexagonal etc., such shape being obtained by correspondingly forming the lamellae.

The present method of insulation will have advantages over and above the purely insulating capacity when used in connection with the transport of liquid methane in large containers. If the container is subject to impacts or subsidences there is a risk that the inertia of the liquid can develop dangerous tensions in the container wall. This is avoided by the buffer eflect of the vapour in the pores, as this becomes compressed and thereby warmed up by the entering liquid. To control this penetration, the pores may be provided with constricted portions, or the pore cross-section at the point of penetration may be reduced by covering all the pore openings by a net.

The invention is illustrated on the attached drawing, in which Figure l is a vertical cross-sectional View of a section of the insulation, and Figures 2 and 3 are plan views of two embodiments of the lamellae. Figure 4 is a view of an assembled unit, and Figure 5 is a sectional view of the insulation mounted on the vertical wall of a container.

The wall of the container is indicated at 1, and the lamellae are indicated at 2. In the embodiment according to Figure 2 the lamellae are corrugated and interconnected in such a way that pores 3 with a circular crosssection are formed between the lamellae. In Figure 3 the lamellae are bent to a zig-zag shape so that the pores are of a quadrilateral cross-section. Further, the shape of the cross-section may be varied in several Ways, and may, for example, be hexagonal, whereby the lamellae are interconnected along planes instead of along lines, as in the two embodiments shown.

From the point of view of mounting of the insulation on the wall, it will be most advantageous to make the insulation in units of suitable size. These can be of quadrilateral or other practical shapes. In Figure 4 a unit is shown in end view which is hexagonal in shape, where 5 indicates a frame which may surround the lamellae.

In order to counteract convection currents it will be found advantageous to arrange the lamellae on a vertical wall, as shown in Figure 5, so that the longitudinal axis of the pores is extending obliquely downwards.

I claim:

1. In combination with a wall of a container for liquids having a boiling point below atmospheric temperature, an insulating structure disposed at the inside of said wall and defining pores which extend inwardly from said wall and open toward the interior of the container, said insulating snucture including a series of successive formed lamellae which, between adjacent lamellae, enclose straight, tubular hollow spaces defining said pores.

2. In combination with a wall of a container for liquids having a boiling point below atmospheric temperature, an insulating structure disposed at the inside of said wall and defining pores which extend inwardly from said wall and open toward the interior of the container, said insulating structure including a plurality of units each formed of profiled lamellae which, between adjacent lamellae, enclose straight, tubular hollow spaces defining said pores.

3. In combination with a wall of a container for liquids having a boiling point below atmospheric temperature, and an insulating structure disposed at the inside of said wall and defining pores which extend inwardly from said wall and open toward the interior of the container, said pores being tubular, hollow spaces sloping downwardly in the direction away from said container wall.

References Cited in the file of this patent UNITED STATES PATENTS 369,796 Kelly Sept. 13, 1887 682,434 Sullivan Sept. 10, 1901 1,533,807 Paterno Apr. 14, 1925 1,724,579 Gunnell .1 Aug. 13, 1929 1,971,308 Gabler Aug. 21, 1934 2,106,828 Chappell Feb. 1, 1938 2,369,006 Banks Feb. 6, 1945 2,441,819 Jensen May 18, 1948 2,477,852 Bacon Aug. 2, 1949 2,676,773 Sanz Apr. 27, 1954 

